Heat resistant thermoplastic articles

ABSTRACT

Disclosed is a molded or extruded thermoplastic article including a polyamide composition including (a) a polyamide resin (b) 0.1 to 10 weight percent of one or more polyhydric alcohols (c) 0 to 3 weight percent of a co-stabilizer selected from the group consisting of secondary aryl amines, hindered amine light stabilizers, and mixtures thereof; (d) 0 to less than 10 weight percent of one or more reinforcement agents; and (e) 0 to 50 weight percent polymeric toughener including a reactive functional group and/or a metal salt of a carboxylic acid; and wherein 4 mm test bars prepared from the polyamide composition, and exposed at an test temperature of 150° C. for a test period of about 1000 hours, have, on average, a retention of strain at break of greater than 80 percent compared with a control exposed at the said test temperature for 72 hours.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. Provisional Application No. 61/137,345, filed on 30 Jul. 2008 and currently pending.

FIELD OF INVENTION

The present invention relates to the field of molded and extruded thermoplastic articles having improved long-term high temperature aging characteristics.

BACKGROUND OF INVENTION

High temperature resins based on polyamides possess desirable chemical resistance, processability and heat resistance. This makes them particularly well suited for demanding high performance applications including automotive and electrical/electronics applications. There is a current and general desire in the automotive field to have high temperature resistant structures since temperatures higher than 150° C., even higher than 200° C., are often reached in underhood areas of automobiles. When plastic parts are exposed to such high temperatures for a prolonged period, such as in automotive under-the-hood applications or in electrical/electronics applications, the mechanical properties generally tend to decrease due to the thermo-oxidation of the polymer. This phenomenon is called heat aging.

In an attempt to improve heat aging characteristics, it has been the conventional practice to add heat stabilizers (also referred as antioxidants) to thermoplastic compositions comprising polyamide resins. Examples of such heat stabilizers include hindered phenol antioxidants, amine antioxidants and phosphorus-based antioxidants. For polyamide compositions, three types of heat stabilizers are conventionally used to retain the mechanical properties of the composition upon exposure to high temperatures. One is the use of phenolic antioxidants optionally combined with a phosphorus based synergist as previously mentioned, the use of aromatic amines optionally combined with a phosphorus based synergist and the third one is the use of copper salts and derivatives. Phenolic antioxidants are known to improve the mechanical/physical properties of the thermoplastic composition up to an aging temperature of 120° C.

Existing technologies lead not only to a poor improvement of long-term heat aging resistance, but also the improved heat aging characteristics are insufficient for more demanding applications involving exposure to higher temperatures such as for example in automotive under-the-hood applications and in electrical/electronics applications.

EP 1041109 discloses a polyamide composition comprising a polyamide resin, a polyhydric alcohol having a melting point of 150 to 280° C., that has good fluidity and mechanical strength and is useful in injection welding techniques.

Another problem is the heat ageing performance of polyamide compositions that generally have low levels of reinforcing agents or none at all. Since unreinforced compositions are generally used in applications that require some flexibility; an important attribute of unreinforced thermoplastics is the retention of strain at break upon heat ageing.

Unfortunately, with existing technologies, molded articles based on flexible polyamide compositions having low levels of reinforcing agent, or none at all, either suffer from an unacceptable deterioration of their mechanical properties upon long-term high temperature exposure or they are very expensive due to the use of high-cost heat stabilizers.

There remains a need for low-cost polyamide compositions that are suitable for manufacturing articles and that exhibit good mechanical properties against long-term high temperature exposure.

SUMMARY OF INVENTION

Disclosed is a molded or extruded thermoplastic article, comprising a polyamide composition comprising

-   -   a) a polyamide resin having a melting point and/or glass         transition;     -   b) 0.1 to 10 weight percent of one or more polyhydric alcohols         having more than two hydroxyl groups and having a number average         molecular weight (M_(n)) of less than 2000;     -   c) 0 to 3 weight percent of a co-stabilizer, having a 10% weight         loss temperature, as determined by thermogravimetric analysis         (TGA), of greater than 30° C. below said melting point of said         polyamide if said melting point is present, or at least 250° C.         if said melting point is not present; said co-stabilizer         selected from the group consisting of secondary aryl amines,         hindered amine light stabilizers, and mixtures thereof;     -   d) 0 to less than 10 weight percent of one or more reinforcement         agents; and     -   e) 0 to 50 weight percent polymeric toughener comprising a         reactive functional group and/or a metal salt of a carboxylic         acid; and         wherein 4 mm test bars prepared from said polyamide composition,         and exposed at an test temperature of 150° C. for a test period         of about 1000 hours, in an atmosphere of air, and tested         according to ISO 527-2/1A, have, on average, a retention of         strain at break of greater than 80 percent, as compared with a         control exposed at said test temperature for 72 hours; and with         the proviso that the polyamide composition contains not more         than 5 weight percent of a plasticizer; and, independently, with         the further proviso that when said polyamide resin is selected         from only a single polyamide having said melting point of at         least 260° C., comprising greater than 95 mole percent         semiaromatic repeat units derived from monomers selected from         the group consisting of: one or more aromatic dicarboxylic         acid(s) having 8 to 20 carbon atoms and one or more aliphatic         diamine(s) having 4 to 20 carbon atoms; said aliphatic         diamine(s) comprise less than 50 mole percent         2-methyl-1,5-pentanediamine.

DETAILED DESCRIPTION

For the purposes of the description, unless otherwise specified, “high-temperature” means a temperature of 150° C.

In the present invention, unless otherwise specified, “long-term” refers to an aging period equal or longer than 1000 hours (h).

A polyamide composition, or a molded or extruded article therefrom, is deemed to have “high heat stability” when 4 mm test specimens, as disclosed herein, when aged in an oven at an test temperature of 150° C. for a test period of 1000 h, in an atmosphere of air, and tested according to ISO 527-2/1A, have, on average, a retention of strain at break of greater than 80 percent, as compared with a control exposed at said test temperature for 72 h. The control herein is identical in composition and shape to that of the 2 mm test bar.

The term “(meth)acrylate” is meant to include acrylate esters and methacrylate esters.

The polyamide resin used in the present invention has a melting point and/or glass transition. Herein melting points and glass transitions are as determined with differential scanning calorimetry (DSC) at a scan rate of 10° C./min in the first heating scan, wherein the melting point is taken at the maximum of the endothermic peak and the glass transition, if evident, is considered the mid-point of the change in enthalpy.

Polyamides are condensation products of one or more dicarboxylic acids and one or more diamines, and/or one or more aminocarboxylic acids, and/or ring-opening polymerization products of one or more cyclic lactams. Suitable cyclic lactams are caprolactam and laurolactam. Polyamides may be fully aliphatic or semi-aromatic.

Fully aliphatic polyamides used in the resin composition of the present invention are formed from aliphatic and alicyclic monomers such as diamines, dicarboxylic acids, lactams, aminocarboxylic acids, and their reactive equivalents. A suitable aminocarboxylic acid is 11-aminododecanoic acid. Suitable lactams are caprolactam and laurolactam. In the context of this invention, the term “fully aliphatic polyamide” also refers to copolymers derived from two or more such monomers and blends of two or more fully aliphatic polyamides. Linear, branched, and cyclic monomers may be used.

Carboxylic acid monomers comprised in the fully aliphatic polyamides include, but are not limited to aliphatic carboxylic acids, such as for example adipic acid (C6), pimelic acid (C7), suberic acid (C8), azelaic acid (C9), decanedioic acid (C10), dodecanedioic acid (C12), tridecanedioic acid (C13), tetradecanedioic acid (C14), and pentadecanedioic acid (C15). Diamines can be chosen among diamines having four or more carbon atoms, including, but not limited to tetramethylene diamine, hexamethylene diamine, octamethylene diamine, decamethylene diamine, dodecamethylene diamine, 2-methylpentamethylene diamine, 2-ethyltetramethylene diamine, 2-methyloctamethylenediamine; trimethylhexamethylenediamine, meta-xylylene diamine, and/or mixtures thereof.

The semi-aromatic polyamide is a homopolymer, a copolymer, a terpolymer or more advanced polymers formed from monomers containing aromatic groups. One or more aromatic carboxylic acids may be terephthalate or a mixture of terephthalate with one or more other carboxylic acids, such as isophthalic acid, phthalic acid, 2-methyl terephthalic acid and naphthalic acid. In addition, the one or more aromatic carboxylic acids may be mixed with one or more aliphatic dicarboxylic acids, as disclosed above. Alternatively, an aromatic diamine such as meta-xylylene diamine (MXD) can be used to provide a semi-aromatic polyamide, an example of which is MXD6, a homopolymer comprising MXD and adipic acid.

Preferred polyamides disclosed herein are homopolymers or copolymers wherein the term copolymer refers to polyamides that have two or more amide and/or diamide molecular repeat units. The homopolymers and copolymers are identified by their respective repeat units. For copolymers disclosed herein, the repeat units are listed in decreasing order of mole % repeat units present in the copolymer. The following list exemplifies the abbreviations used to identify monomers and repeat units in the homopolymer and copolymer polyamides (PA):

-   HMD hexamethylene diamine (or 6 when used in combination with a     diacid) -   T Terephthalic acid -   AA Adipic acid -   DMD Decamethylenediamine -   6     -Caprolactam -   DDA Decanedioic acid -   DDDA Dodecanedioic acid -   I Isophthalic acid -   MXD meta-xylylene diamine -   TMD 1,4-tetramethylene diamine -   4T polymer repeat unit formed from TMD and T -   6T polymer repeat unit formed from HMD and T -   DT polymer repeat unit formed from 2-MPMD and T -   MXD6 polymer repeat unit formed from MXD and AA -   66 polymer repeat unit formed from HMD and AA -   10T polymer repeat unit formed from DMD and T -   410 polymer repeat unit formed from TMD and DDA -   510 polymer repeat unit formed from 1,5-pentanediamine and DDA -   610 polymer repeat unit formed from HMD and DDA -   612 polymer repeat unit formed from HMD and DDDA -   6 polymer repeat unit formed from     -caprolactam -   11 polymer repeat unit formed from 11-aminoundecanoic acid -   12 polymer repeat unit formed from 12-aminododecanoic acid

Note that in the art the term “6” when used alone designates a polymer repeat unit formed from

-caprolactam. Alternatively “6” when used in combination with a diacid such as T, for instance 6T, the “6” refers to HMD. In repeat units comprising a diamine and diacid, the diamine is designated first. Furthermore, when “6” is used in combination with a diamine, for instance 66, the first “6” refers to the diamine HMD, and the second “6” refers to adipic acid. Likewise, repeat units derived from other amino acids or lactams are designated as single numbers designating the number of carbon atoms.

In one embodiment the polyamide composition comprises a one or more polyamides selected from the group consisting of

-   -   Group (I) Polyamides having said melting point of less than 210°         C., and comprising an aliphatic or semiaromatic polyamide         selected from the group poly(pentamethylene decanediamide)         (PA510), poly(pentamethylene dodecanediamide) (PA512),         poly(ε-caprolactam/hexamethylene hexanediamide) (PA6/66),         poly(ε-caprolactam/hexamethylene decanediamide) (PA6/610),         poly(ε-caprolactam/hexamethylene dodecanediamide) (PA6/612),         poly(hexamethylene tridecanediamide) (PA613), poly(hexamethylene         pentadecanediamide) (PA615), poly(ε-caprolactam/tetramethylene         terephthalamide) (PA6/4T), poly(ε-caprolactam/hexamethylene         terephthalamide) (PA6/6T), poly(ε-caprolactam/decamethylene         terephthalamide) (PA6/10T), poly(ε-caprolactam/dodecamethylene         terephthalamide) (PA6/12T), poly(hexamethylene         decanediamide/hexamethylene terephthalamide) (PA610/6T),         poly(hexamethylene dodecanediamide/hexamethylene         terephthalamide) (PA612/6T), poly(hexamethylene         tetradecanediamide/hexamethylene terephthalamide) (PA614/6T),         poly(ε-caprolactam/hexamethylene isophthalamide/hexamethylene         terephthalamide) (PA6/6I/6T), poly(ε-caprolactam/hexamethylene         hexanediamide/hexamethylene decanediamide) (PA6/66/610),         poly(ε-caprolactam/hexamethylene hexanediamide/hexamethylene         dodecanediamide) (PA6/66/612), poly(ε-caprolactam/hexamethylene         hexanediamide/hexamethylene decanediamide/hexamethylene         dodecanediamide) (PA6/66/610/612), poly(2-methylpentamethylene         hexanediamide/hexamethylene hexanediamide/hexamethylene         terephthamide) (PA D6/66//6T), poly(2-methylpentamethylene         hexanediamide/hexamethylene hexanediamide/) (PA D6/66),         poly(decamethylene decanediamide) (PA1010), poly(decamethylene         dodecanediamide) (PA1012), poly(decamethylene         decanediamide/decamethylene terephthalamide) (PA1010/10T)         poly(decamethylene decanediamide/dodecamethylene         decanediamide/decamethylene terephthalamide/dodecamethylene         terephthalamide (PA1010/1210/10T/12T),         poly(11-aminoundecanamide) (PA11),         poly(11-aminoundecanamide/tetramethylene terephthalamide)         (PA11/4T), poly(11-aminoundecanamide/hexamethylene         terephthalamide) (PA11/6T),         poly(11-aminoundecanamide/decamethylene terephthalamide)         (PA11/10T), poly(11-aminoundecanamide/dodecamethylene         terephthalamide) (PA11/12T), poly(12-aminododecanamide) (PA12),         poly(12-aminododecanamide/tetramethylene terephthalamide)         (PA12/4T), poly(12-aminododecanamide/hexamethylene         terephthalamide) (PA12/6T),         poly(12-aminododecanamide/decamethylene terephthalamide)         (PA12/10T) poly(dodecamethylene dodecanediamide) (PA1212), and         poly(dodecamethylene dodecanediamide/dodecamethylene         dodecanediamide/dodecamethylene terephthalamide)) (PA1212/12T);     -   Group (II) Polyamides having said melting point of at least 210°         C., and comprising an aliphatic polyamide selected from the         group consisting of poly(tetramethylene hexanediamide) (PA46),         poly(ε-caprolactam) (PA 6), poly(hexamethylene         hexanediamide/(ε-caprolactam/) (PA 66/6) poly(hexamethylene         hexanediamide) (PA 66), poly(hexamethylene         hexanediamide/hexamethylene decanediamide) (PA66/610),         poly(hexamethylene hexanediamide/hexamethylene dodecanediamide)         (PA66/612), poly(hexamethylene hexanediamide/decamethylene         decanediamide) (PA66/1010), poly(hexamethylene decanediamide)         (PA610), poly(hexamethylene dodecanediamide) (PA612),         poly(hexamethylene tetradecanediamide) (PA614),         poly(hexamethylene hexadecanediamide) (PA616), and         poly(tetramethylene hexanediamide/2-methylpentamethylene         hexanediamide) (PA46/D6);     -   Group (III) Polyamides having said melting point of at least         210° C., and comprising         -   (aa) about 20 to about 35 mole percent semiaromatic repeat             units derived from monomers selected from one or more of the             group consisting of:             -   (i) aromatic dicarboxylic acids having 8 to 20 carbon                 atoms and aliphatic diamines having 4 to 20 carbon                 atoms; and         -   (bb) about 65 to about 80 mole percent aliphatic repeat             units derived from monomers selected from one or more of the             group consisting of:             -   (ii) an aliphatic dicarboxylic acid having 6 to 20                 carbon atoms and said aliphatic diamine having 4 to 20                 carbon atoms; and             -   (iii) a lactam and/or aminocarboxylic acid having 4 to                 20 carbon atoms;         -   Group (IV) Polyamides comprising         -   (cc) about 50 to about 95 mole percent semiaromatic repeat             units derived from monomers selected from one or more of the             group consisting of:             -   (i) aromatic dicarboxylic acids having 8 to 20 carbon                 atoms and aliphatic diamines having 4 to 20 carbon                 atoms; and         -   (dd) about 5 to about 50 mole percent aliphatic repeat units             derived from monomers selected from one or more of the group             consisting of:             -   (ii) an aliphatic dicarboxylic acid having 6 to 20                 carbon atoms and said aliphatic diamine having 4 to 20                 carbon atoms; and             -   (iii) a lactam and/or aminocarboxylic acid having 4 to                 20 carbon atoms;         -   Group (V) Polyamides having said melting point of at least             260° C., and comprising         -   (ee) greater than 95 mole percent semiaromatic repeat units             derived from monomers selected from one or more of the group             consisting of:             -   (i) aromatic dicarboxylic acids having 8 to 20 carbon                 atoms and aliphatic diamines having 4 to 20 carbon                 atoms; and         -   (ff) less than 5 mole percent aliphatic repeat units derived             from monomers selected from one or more of the group             consisting of:             -   (ii) an aliphatic dicarboxylic acid having 6 to 20                 carbon atoms and said aliphatic diamine having 4 to 20                 carbon atoms;             -   (iii) a lactam and/or aminocarboxylic acid having 4 to                 20 carbon atoms; and     -   Group (VI) Polyamides having no melting point selected from the         group consisting of poly(hexamethylene         isophthalamide/hexamethylene terephthalamide) (6I/6T) and         poly(hexamethylene isophthalamide/hexamethylene         terephthalamide/hexamethylene hexanediamide) (6I/6T/66).

Group (I) Polyamides may have semiaromatic repeat units to the extent that the melting point is less than 210° C. and generally the semiaromatic polyamides of the group have less than 40 mole percent semiaromatic repeat units. Semiaromatic repeat units are defined as those derived from monomers selected from one or more of the group consisting of: aromatic dicarboxylic acids having 8 to 20 carbon atoms and aliphatic diamines having 4 to 20 carbon atoms.

One embodiment is a molded or extruded thermoplastic article wherein said polyamide resin is selected from Group (I) Polyamides and wherein said test temperature is at least 150° C. for a test period of at least 1000 hours and said retention of strain is greater than 80%.

One embodiment is a molded or extruded thermoplastic article wherein said polyamide resin is selected from Group (II) Polyamides and wherein said test temperature is at least 150° C. for a test period of at least 1000 hours and said retention of strain is greater than 80%.

Another embodiment is a molded or extruded thermoplastic article wherein said polyamide resin is selected from Group (III) Polyamides are selected from the group consisting of poly(tetramethylene hexanediamide/tetramethylene terephthalamide) (PA46/4T), poly(tetramethylene hexanediamide/hexamethylene terephthalamide) (PA46/6T), poly(tetramethylene hexanediamide/2-methylpentamethylene hexanediamide/decamethylene terephthalamide)_PA46/D6/10T), poly(hexamethylene hexanediamide/hexamethylene terephthalamide) (PA66/6T), poly(hexamethylene hexanediamide/hexamethylene isophthalamide/hexamethylene terephthalamide PA66/6I/6T, and poly(hexamethylene hexanediamide/2-methylpentamethylene hexanediamide/hexamethylene terephthalamide (PA66/D6/6T); and a most preferred Group (III) Polyamide is PA 66/6T.

Another embodiment is a molded or extruded thermoplastic article wherein said polyamide resin is selected from Group (IV) Polyamides selected from the group consisting of poly(tetramethylene terephthalamide/hexamethylene hexanediamide) (PA4T/66), poly(tetramethylene terephthalamide/ε-caprolactam) (PA4T/6), poly(tetramethylene terephthalamide/hexamethylene dodecanediamide) (PA4T/612), poly(tetramethylene terephthalamide/2-methylpentamethylene hexanediamide/hexamethylene hexanediamide) (PA4T/D6/66), poly(hexaamethylene terephthalamide/2-methylpentamethylene terephthalamide/hexamethylene hexanediamide) (PA6T/DT/66), poly(hexamethylene terephthalamide/hexamethylene hexanediamide) PA6T/66, poly(hexaamethylene terephthalamide/hexamethylene decanediamide) (PA6T/610), poly(hexamethylene terephthalamide/hexamethylene tetradecanediamide) (PA6T/614), poly(nonamethylene terephthalamide/nonamethylene decanediamide) (PA9T/910), poly(nonamethylene terephthalamide/nonamethylene dodecanediamide) (PA9T/912), poly(nonamethylene terephthalamide/11-aminoundecanamide) (PA9T/11), poly(nonamethylene terephthalamide/12-aminododecanamide) (PA9T/12), poly(decamethylene terephthalamide/11-aminoundecanamide) (PA 10T/11), poly(decamethylene terephthalamide/12-aminododecanamide) (PA10T/12) poly(decamethylene terephthalamide/decamethylene decanediamide) (PA10T/1010), poly(decamethylene terephthalamide/decamethylene dodecanediamide) (PA10T/1012), poly(decamethylene terephthalamide/tetramethylene hexanediamide) (PA10T/46), poly(decamethylene terephthalamide/ε-caprolactam) (PA10T/6), poly(decamethylene terephthalamide/hexamethylene hexanediamide) (PA10T/66), poly(dodecamethylene terephthalamide/dodecamethylene dodecanediamide) (PA12T/1212), poly(dodecamethylene terephthalamide/ε-caprolactam) (PA12T/6), and poly(dodecamethylene terephthalamide/hexamethylene hexanediamide) (PA12T/66); and a most preferred Group (IV) Polyamide is PA6T/66.

Another embodiment is a molded or extruded thermoplastic article wherein said polyamide resin is selected from Group (V) Polyamides selected from the group consisting of poly(tetramethylene terephthalamide/2-methylpentamethylene terephthalamide) PA4T/DT, poly(tetramethylene terephthalamide/hexamethylene terephthalamide) PA4T/6T, poly(tetramethylene terephthalamide/decamethylene terephthalamide) PA4T/10T, poly(tetramethylene terephthalamide/dodecamethylene terephthalamide)PA4T/12T, poly(tetramethylene terephthalamide/2-methylpentamethylene terephthalamide/hexamethylene terephthalamide) (PA4T/DT/6T), poly(tetramethylene terephthalamide/hexamethylene terephthalamide/2-methylpentamethylene terephthalamide) (PA4T/6T/DT), poly(hexamethylene terephthalamide/2-methylpentamethylene terephthalamide) (PA6T/DT), poly(hexamethylene hexanediamide/hexamethylene isophthalamide) (PA 6T/6I), poly(hexamethylene terephthalamide/decamethylene terephthalamide) PA6T/10T, poly(hexamethylene terephthalamide/dodecamethylene terephthalamide) (PA6T/12T), poly(hexamethylene terephthalamide/2-methylpentamethylene terephthalamide/poly(decamethylene terephthalamide) (PA6T/DT/10T), poly(hexamethylene terephthalamide/decamethylene terephthalamide/dodecamethylene terephthalamide) (PA6T/10T/12T), poly(decamethylene terephthalamide) (PA10T), poly(decamethylene terephthalamide/tetramethylene terephthalamide) (PA10T/4T), poly(decamethylene terephthalamide/2-methylpentamethylene terephthalamide) (PA10T/DT), poly(decamethylene terephthalamide/dodecamethylene terephthalamide) (PA10T/12T), poly(decamethylene terephthalamide/2-methylpentamethylene terephthalamide/(decamethylene terephthalamide) (PA10T/DT/12T), poly(dodecamethylene terephthalamide) (PA12T), poly(dodecamethylene terephthalamide)/tetramethylene terephthalamide) (PA12T/4T), poly(dodecamethylene terephthalamide)/hexamethylene terephthalamide) PA12T/6T, poly(dodecamethylene terephthalamide)/decamethylene terephthalamide) (PA12T/10T), and poly(dodecamethylene terephthalamide)/2-methylpentamethylene terephthalamide) (PA12T/DT); with the proviso that when said Group (V) Polyamide is selected from only a single polyamide having said melting point of at least 260° C., and comprising greater than 95 mole percent semiaromatic repeat units derived from monomers selected from one or more of the group consisting of aromatic dicarboxylic acids having 8 to 20 carbon atoms and aliphatic diamines having 4 to 20 carbon atoms; said aliphatic diamine(s) comprise less than 50 mole percent 2-methyl-1,5-pentanediamine.

In various embodiments the polyamide is a Group (III) Polyamide, Group (IV) Polyamide, Group (V) Polyamide or Group (VI) Polyamide, respectively.

The polyamides may also be blends of two or more polyamides. Preferred blends include those selected from the group consisting of Group (I) and Group (II) Polyamides; Group (I) and (III) Polyamide, Group (I) and Group (VI) Polyamides, Group (II) and Group (III) Polyamides, Group (II) and Group (IV) Polyamides, Group (II) and Group (V) Polyamides, Group (II) and Group (VI) Polyamides, Group (III) and Group (VI) Polyamides, and Group (IV) and Group (V) Polyamides.

A preferred blend includes Group (II) and Group (V) Polyamides, and a specific preferred blend includes poly(hexamethylene hexanediamide) (PA 66) and poly(hexamethylene terephthalamide/2-methylpentamethylene terephthalamide) (PA 6T/DT).

Another preferred blend includes Group (II) and Group (III) Polyamides and a specific preferred blend includes poly(ε-caprolactam) (PA6) and poly(hexamethylene hexanediamide/hexamethylene terephthalamide (PA66/6T).

The molded or extruded thermoplastic article comprises 0.1 to 10 weight percent of one or more polyhydric alcohols having more than two hydroxyl groups and having a number average molecular weight (M_(n)) of less than 2000 as determined for polymeric materials with gel permeation chromatography (GPC).

Polyhydric alcohols may be selected from aliphatic hydroxylic compounds containing more than two hydroxyl groups, aliphatic-cycloaliphatic compounds containing more than two hydroxyl groups, cycloaliphatic compounds containing more than two hydroxyl groups, aromatic and saccharides.

An aliphatic chain in the polyhydric alcohol can include not only carbon atoms but also one or more hetero atoms which may be selected, for example, from nitrogen, oxygen and sulphur atoms. A cycloaliphatic ring present in the polyhydric alcohol can be monocyclic or part of a bicyclic or polycyclic ring system and may be carbocyclic or heterocyclic. A heterocyclic ring present in the polyhydric alcohol can be monocyclic or part of a bicyclic or polycyclic ring system and may include one or more hetero atoms which may be selected, for example, from nitrogen, oxygen and sulphur atoms. The one or more polyhydric alcohols may contain one or more substituents, such as ether, carboxylic acid, carboxylic acid amide or carboxylic acid ester groups.

Examples of polyhydric alcohol containing more than two hydroxyl groups include, without limitation, triols, such as glycerol, trimethylolpropane, 2,3-di-(2′-hydroxyethyl)-cyclohexan-1-ol, hexane-1,2,6-triol, 1,1,1-tris-(hydroxymethyl)ethane, 3-(2′-hydroxyethoxy)-propane-1,2-diol, 3-(2′-hydroxypropoxy)-propane-1,2-diol, 2-(2′-hydroxyethoxy)-hexane-1,2-diol, 6-(2′-hydroxypropoxy)-hexane-1,2-diol, 1,1,1-tris-[(2′-hydroxyethoxy)-methyl]-ethane, 1,1,1-tris-[(2′-hydroxypropoxy)-methyl]-propane, 1,1,1-tris-(4′-hydroxyphenyl)-ethane, 1,1,1-tris-(hydroxyphenyl)-propane, 1,1,3-tris-(dihydroxy-3-methylphenyl)-propane, 1,1,4-tris-(dihydroxyphenyl)-butane, 1,1,5-tris-(hydroxyphenyl)-3-methylpentane, di-trimethylopropane, trimethylolpropane ethoxylates, or trimethylolpropane propoxylates; polyols such as pentaerythritol, dipentaerythritol, and tripentaerythritol; and saccharides, such as cyclodextrin, D-mannose, glucose, galactose, sucrose, fructose, xylose, arabinose, D-mannitol, D-sorbitol, D-or L-arabitol, xylitol, iditol, talitol, allitol, altritol, guilitol, erythritol, threitol, and D-gulonic-y-lactone; and the like.

Preferred polyhydric alcohols include those having a pair of hydroxyl groups which are attached to respective carbon atoms which are separated one from another by at least one atom. Especially preferred polyhydric alcohols are those in which a pair of hydroxyl groups is attached to respective carbon atoms which are separated one from another by a single carbon atom.

Preferably, the polyhydric alcohol used in the thermoplastic composition is pentaerythritol, dipentaerythritol, tripentaerythritol, di-trimethylolpropane, D-mannitol, D-sorbitol and xylitol. More preferably, the polyhydric alcohol used is dipentaerythritol and/or tripentaerythritol. A most preferred polyhydric alcohol is dipentaerythritol.

In various embodiments the content of said polyhydric alcohol in the thermoplastic composition is 0.1 to less than 10 weight percent, preferably 0.25-8 weight percent, more preferably 0.25-5 weight percent and most preferably 1-4 weight percent; based on the total weight of said thermoplastic composition.

The molded or extruded thermoplastic article comprises less than 10 weight percent, preferably 5 weight percent % or less of one or more reinforcement agents. In a preferred embodiment the molded or extruded thermoplastic article includes no reinforcement agent. When a reinforcement agent is present, it may be any filler, but is preferably selected from the group consisting calcium carbonate, glass fibers with circular and noncircular cross-section, glass flakes, glass beads, carbon fibers, talc, mica, wollastonite, calcined clay, kaolin, diatomite, magnesium sulfate, magnesium silicate, barium sulfate, titanium dioxide, sodium aluminum carbonate, barium ferrite, potassium titanate and mixtures thereof.

The molded or extruded thermoplastic article may further comprise 0 to 50 weight percent of a polymeric toughener comprising a reactive functional group and/or a metal salt of a carboxylic acid. In one embodiment the molded or extruded thermoplastic article comprises 2 to 20 weight percent polymeric toughener selected from the group consisting of: a copolymer of ethylene, glycidyl(meth)acrylate, and optionally one or more (meth)acrylate esters; an ethylene/α-olefin or ethylene/α-olefin/diene copolymer grafted with an unsaturated carboxylic anhydride; a copolymer of ethylene, 2-isocyanatoethyl(meth)acrylate, and optionally one or more (meth)acrylate esters; and a copolymer of ethylene and acrylic acid reacted with a Zn, Li, Mg or Mn compound to form the corresponding ionomer.

The molded or extruded thermoplastic article comprises 0 to 3 weight percent of a co-stabilizer that is useful in combination with the polyhdric alcohol, in affecting the long-term heat stability of article. Preferred co-stabilizers have a 10% weight loss temperature, as determined by TGA, of greater than 30° C. below said melting point of said polyamide if said melting point is present, or at least 250° C. if said melting point is not present; and said co-stabilizers are selected from the group consisting of secondary aryl amines, hindered amine light stabilizers, and mixtures thereof.

For the purposes of this invention, TGA weight loss will be determined according to ASTM D 3850-94, using a heating rate of 10° C./min, in air purge stream, with an appropriate flow rate of 0.8 mL/second. The co-stabilizer preferably has a 10% weight loss temperature, as determined by TGA, of at least 270° C., and more preferably 290° C., 320° C., and 340° C., and most preferably at least 350° C. The one or more co-stabilizers preferably are present from at or about 0.1 to 3 weight percent, and more preferably at or about 0.1 to at or about 1 weight percent, or more preferably from at or about 0.1 to at or about 0.7 weight percent, based on the total weight of the polyamide composition.

Secondary aryl amines useful in the invention are high molecular weight organic compound having low volatility. Preferably, the high molecular weight organic compound will be selected from the group consisting of secondary aryl amines further characterized as having a molecular weight of at least 260 g/mol and preferably at least 350 g/mol, together with a 10% weight loss temperature as determined by TGA of at least 290° C., preferably at least 300° C., 320° C., 340° C., and most preferably at least 350° C.

By secondary aryl amine is meant an amine compound that contains two carbon radicals chemically bound to a nitrogen atom where at least one, and preferably both carbon radicals, are aromatic. Preferably, at least one of the aromatic substituents, such as, for example, a phenyl, naphthyl or heteroaromatic group, is substituted with at least one substituent, preferably containing 1 to about 20 carbon atoms.

Examples of suitable secondary aryl amines include 4,4′di(α,α-dimethylbenzyl)diphenylamine available commercially as Naugard 445 from Uniroyal Chemical Company, Middlebury, Conn.; the secondary aryl amine condensation product of the reaction of diphenylamine with acetone, available commercially as Aminox from Uniroyal Chemical Company; and para-(paratoluenesulfonylamido)diphenylamine also available from Uniroyal Chemical Company as Naugard SA. Other suitable secondary aryl amines include N,Nα-di-(2-naphthyl)-p-phenylenediamine, available from ICI Rubber Chemicals, Calcutta, India. Other suitable secondary aryl amines include 4,4′-bis(α,α′-tertiaryoctyl)diphenylamine, 4,4′-bis(α-methylbenzhydryl)diphenylamine, and others from EP 0509282 B1.

The molded or extruded thermoplastic article may have at least one co-stabilizer selected from one or more secondary aryl amines. Preferably the one or more secondary aryl amines is present at about 0.25 to 1.0 weight percent and more preferably 0.25 to about 0.9 weight percent, based on the total weight of the polyamide composition.

The hindered amine light stabilizers (HALS) may be one or more hindered amine type light stabilizers (HALS). HALS are compounds of the following general formulas and combinations thereof:

In these formulas, R₁ up to and including R₅ are independent substituents. Examples of suitable substituents are hydrogen, ether groups, ester groups, amine groups, amide groups, alkyl groups, alkenyl groups, alkynyl groups, aralkyl groups, cycloalkyl groups and aryl groups, in which the substituents in turn may contain functional groups; examples of functional groups are alcohols, ketones, anhydrides, imines, siloxanes, ethers, carboxyl groups, aldehydes, esters, amides, imides, amines, nitriles, ethers, urethanes and any combination thereof. A hindered amine light stabilizer may also form part of a polymer or oligomer.

Preferably, the HALS is a compound derived from a substituted piperidine compound, in particular any compound derived from an alkyl-substituted piperidyl, piperidinyl or piperazinone compound, and substituted alkoxypiperidinyl compounds. Examples of such compounds are: 2,2,6,6-tetramethyl-4-piperidone; 2,2,6,6-tetrametyl-4-piperidinol; bis-(1,2,2,6,6-pentamethyl piperidyl)-(3′,5′-di-tert-butyl-4′-hydroxybenzyl)butylmalonate; di-(2,2,6,6-tetramethyl-4-piperidyl)sebacate (Tinuvin® 770, MW 481); oligomer of N-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol and succinic acid (Tinuvin® 622); oligomer of cyanuric acid and N,N-di(2,2,6,6-tetramethyl-4-piperidyl)-hexamethylene diamine; bis-(2,2,6,6-tetramethyl-4-piperidinyl)succinate; bis-(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl)sebacate (Tinuvin® 123); bis-(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate (Tinuvin® 765); Tinuvin® 144; Tinuvin® XT850; tetrakis-(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butane tetracarboxylate; N,N′-bis-(2,2,6,6-tetramethyl-4-piperidyl)-hexane-1,6-diamine (Chimasorb® T5); N-butyl-2,2,6,6-tetramethyl-4-piperidinamine; 2,2′-[(2,2,6,6-tetramethyl-piperidinyl)-imino]-bis-[ethanol]; poly((6-morpholine-S-triazine-2,4-diyl)(2,2,6,6-tetramethyl-4-piperidinyl)-iminohexamethylene-(2,2,6,6-tetramethyl-4-piperidinyl)-imino) (Cyasorb® UV 3346); 5-(2,2,6,6-tetramethyl-4-piperidinyl)-2-cyclo-undecyl-oxazole) (Hostavin® N20); 1,1′-(1,2-ethane-di-yl)-bis-(3,3′,5,5′-tetramethyl-piperazinone); 8-acetyl-3-dothecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro(4,5)decane-2,4-dione; polymethylpropyl-3-oxy-[4(2,2,6,6-tetramethyl)-piperidinyl]siloxane (Uvasil® 299); 1,2,3,4-butane-tetracarboxylic acid-1,2,3-tris(1,2,2,6,6-pentamethyl-4-piperidinyl)-4-tridecylester; copolymer of alpha-methylstyrene-N-(2,2,6,6-tetramethyl-4-piperidinyl)maleimide and N-stearyl maleimide; 1,2,3,4-butanetetracarboxylic acid, polymer with beta,beta,beta′,beta′-tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol, 1,2,2,6,6-pentamethyl-4-piperidinyl ester (Mark® LA63); 2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol, beta,beta,beta′,beta′-tetramethyl-polymer with 1,2,3,4-butanetetracarboxylic acid, 2,2,6,6-tetramethyl-4-piperidinyl ester (Mark® LA68); D-glucitol, 1,3:2,4-bis-O-(2,2,6,6-tetramethyl-4-piperidinylidene)-(HALS 7); oligomer of 7-oxa-3,20-diazadispiro[5.1.11.2]-heneicosan-21-one-2,2,4,4-tetramethyl-20-(oxiranylmethyl) (Hostavin® N30); propanedioic acid, [(4-methoxyphenyl)methylene]-,bis(1,2,2,6,6-pentamethyl-4-piperidinyl)ester (Sanduvor® PR 31); formamide, N,N′-1,6-hexanediylbis[N-(2,2,6,6-tetramethyl-4-piperidinyl (Uvinul® 4050H); 1,3,5-triazine-2,4,6-triamine, N,N′″-[1,2-ethanediylbis[[[4,6-bis[butyl(1,2,2,6,6-pentamethyl-4-piperidinyl)amino]-1,3,5-triazine-2-yl]imino]-3,1-propanediyl]]-bis[N′,N″-dibutyl-N′,N″-bis(1,2,2,6,6-pentamethyl-4-piperidinyl) (Chimassorb® 119 MW 2286); poly[[6-[(1,1,3,33-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-peperidinyl)-imino]-1,6-hexanediyl [(2,2,6,6-tetramethyl-4-piperidinyl)imino]] (Chimassorb® 944 MW 2000-3000); 1,5-dioxaspiro (5,5) undecane 3,3-dicarboxylic acid, bis(2,2,6,6-tetramethyl-4-peridinyl)ester (Cyasorb® UV-500); 1,5-dioxaspiro(5,5)undecane 3,3-dicarboxylic acid, bis(1,2,2,6,6-pentamethyl-4-peridinyl)ester (Cyasorb® UV-516); N-2,2,6,6-tetramethyl-4-piperidinyl-N-amino-oxamide; 4-acryloyloxy-1,2,2,6,6-pentamethyl-4-piperidine. 1,5,8,12-tetrakis[2′,4′-bis(1″,2″,2″,6″,6″-pentamethyl-4″-piperidinyl(butyl)amino)-1′, 3′,5′-triazine-6′-yl]-1,5,8,12-tetraazadodecane; HALS PB-41 (Clariant Huningue S. A.); Nylostab® S-EED (Clariant Huningue S. A.); 3-dodecyl-1-(2,2,6,6-tetramethyl-4-piperidyl)-pyrrolidin-2,5-dione; Uvasorb® HA88; 1,1′-(1,2-ethane-di-yl)-bis-(3,3′,5,5′-tetra-methyl-piperazinone) (Good-rite® 3034); 1,1′1″-(1,3,5-triazine-2,4,6-triyltris((cyclohexylimino)-2,1-ethanediyl)tris(3,3,5,5-tetramethylpiperazinone) (Good-rite® 3150) and; 1,1′,1″-(1,3,5-triazine-2,4,6-triyltris((cyclohexylimino)-2,1-ethanediyl)tris(3,3,4,5,5-tetramethylpiperazinone) (Good-rite® 3159). Tinuvin® and Chimassorb® materials are available from Ciba Specialty Chemicals; Cyasorb® materials are available from Cytec Technology Corp.; Uvasil® materials are available from Great Lakes Chemical Corp.; Saduvor®, Hostavin®, and Nylostab® materials are available from Clariant Corp.; Uvinul® materials are available from BASF; Uvasorb® materials are available from Partecipazioni Industriali; and Good-rite® materials are available from B.F. Goodrich Co. Mark® materials are available from Asahi Denka Co.

Preferred HALS include high-molecular weight oligomeric or polymeric HALS having a molecular weight of more than about 1000, and preferably more than about 2000.

Other specific HALS are selected from the group consisting or di-(2,2,6,6-tetramethyl-4-piperidyl)sebacate (Tinuvin® 770, MW 481) Nylostab® S-EED (Clariant Huningue S. A.); 1,3,5-triazine-2,4,6-triamine, N,N′″-[1,2-ethanediylbis[[[4,6-bis[butyl(1,2,2,6,6-pentamethyl-4-piperidinyl)amino]-1,3,5-triazine-2-yl]imino]-3,1-propanediyl]]-bis[N′,N″-dibutyl-N′,N″-bis(1,2,2,6,6-pentamethyl-4-piperidinyl) (Chimassorb® 119 MW 2286); and poly[[6-[(1,1,3,33-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-peperidinyl)-imino]-1,6-hexanediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]] (Chimassorb® 944 MW 2000-3000).

The molded or extruded thermoplastic article may have at least one co-stabilizer selected from one or more HALS. Preferably the one or more HALS is present at about 0.25 to 1.0 weight percent and more preferably 0.25 to about 0.9 weight percent, based on the total weight of the polyamide composition.

Mixtures of secondary aryl amines and HALS may be used. A preferred embodiment comprises at least two co-stabilizers, at least one selected from the secondary aryl amines; and at least one selected from the group of HALS, as disclosed above, wherein the total weight percent of the mixture of co-stabilizers is at least 0.5 weight percent, and preferably at least 0.9 weight percent.

In the present invention, the polyamide composition may also comprise other additives commonly used in the art, such as other heat stabilizers or antioxidants, antistatic agents, blowing agents, lubricants, plasticizers, and colorant and pigments.

Other heat stabilizers include copper stabilizers and hindered phenols, and mixtures thereof.

A significant advantage of the molded or extruded thermoplastic articles of the invention is that high thermal stability, as measured under AOA conditions disclosed herein, is provided without the use of conventional copper heat stabilizers. Copper heat stabilizers tend to act as corrosive agents over long periods of time at elevated temperatures; and in some environments actually cause degradation of semiaromatic polymers. Thus, another embodiment is molded or extruded thermoplastic article wherein said polyamide composition comprises less than 25 ppm copper as determined with atomic absorption spectroscopy.

The polyamide composition may comprise plasticizers. A plasticizer will preferably be miscible with the polyamide. Examples of suitable plasticizers include sulfonamides, preferably aromatic sulfonamides such as benzenesulfonamides and toluenesulfonamides. Examples of suitable sulfonamides include N-alkyl benzenesulfonamides and toluenesufonamides, such as N-butylbenzenesulfonamide, N-(2-hydroxypropyl)benzenesulfonamide, N-ethyl-o-toluenesulfonamide, N-ethyl-p-toluenesulfonamide, o-toluenesulfonamide, p-toluenesulfonamide, and the like. Preferred are N-butylbenzenesulfonamide, N-ethyl-o-toluenesulfonamide, and N-ethyl-p-toluenesulfonamide.

The plasticizer may be incorporated into the composition by melt-blending the polymer with plasticizer and, optionally, other ingredients, or during polymerization. If the plasticizer is incorporated during polymerization, the polyamide monomers are blended with one or more plasticizers prior to starting the polymerization cycle and the blend is introduced to the polymerization reactor. Alternatively, the plasticizer can be added to the reactor during the polymerization cycle.

If a plasticizer is present in the polyamide composition, the polyamide composition contains no more than 5 weight percent of plasticizer.

Herein the thermoplastic composition is a mixture by melt-blending, in which all polymeric ingredients are adequately mixed, and all non-polymeric ingredients are adequately dispersed in a polymer matrix. Any melt-blending method may be used for mixing polymeric ingredients and non-polymeric ingredients of the present invention. For example, polymeric ingredients and non-polymeric ingredients may be fed into a melt mixer, such as single screw extruder or twin screw extruder, agitator, single screw or twin screw kneader, or Banbury mixer, and the addition step may be addition of all ingredients at once or gradual addition in batches. When the polymeric ingredient and non-polymeric ingredient are gradually added in batches, a part of the polymeric ingredients and/or non-polymeric ingredients is first added, and then is melt-mixed with the remaining polymeric ingredients and non-polymeric ingredients that are subsequently added, until an adequately mixed composition is obtained. If a reinforcing filler presents a long physical shape (for example, a long glass fiber), drawing extrusion molding may be used to prepare a reinforced composition.

The thermoplastic composition having a polyhydric alcohol having two or more hydroxyl groups, as disclosed above, is useful in increasing long-term thermal stability at high temperatures of molded or extruded articles made therefrom. The long-term thermal stability of the articles can be assessed by air oven ageing (AOA) of 4 mm thick test samples at various test temperatures for various test periods of time. The test temperature for the composition disclosed herein is at 150° C. and for about 1000 hours test period. The term “at 150° C.” refers to the nominal temperature of the environment to which the test bars are exposed; with the understanding that the actual temperature may vary by ±2° C. from the nominal test temperature.

The test samples, after air oven ageing, are tested for tensile strength and strain at break, according to ISO 527-2/1A test method; and compared with a control aged at said test temperature for 72 hours. Ageing the control at the test temperature for 72 hours may allow crystallization to equilibrate in the molded test specimens, and thus may allow more reliable measure of AOA performance. The comparison with the controls provides the retention of strain at break, and thus the various compositions can be assessed as to long-term high temperature ageing performance.

In various embodiments the molded 4 mm test specimens of polyamide composition, as disclosed herein, have a retention of strain at break of at least 80% after AOA at 150° C. for 1000 hours and preferably at least 90%, based upon comparison with controls exposed at said test temperature for 72 hours.

In another embodiment the molded 4 mm test specimens of polyamide composition, as disclosed herein, have a retention of strain at break of at least 50% after AOA at 150° C. for about 2000 hours and preferably at least 75%, based upon comparison with controls exposed at said test temperature for 72 hours

In another aspect, the present invention relates a use of the above disclosed thermoplastic compositions for high temperature applications.

In another aspect, the present invention relates to a method for manufacturing an article by shaping the thermoplastic composition of the invention. Examples of articles are films or laminates, automotive parts or engine parts or electrical/electronics parts. By “shaping”, it is meant any shaping technique, such as for example extrusion, injection moulding, thermoform moulding, compression moulding or blow moulding. Preferably, the article is shaped by injection moulding or blow moulding.

The molded or extruded thermoplastic articles disclosed herein may have application in automotive and other components that meet one or more of the following requirements: high chemical resistance to polar chemicals such as such as zinc chloride and calcium chloride, high impact requirements; resistance to high temperature; resistance to oil and fuel environment; resistance to chemical agents such as coolants; low permeability to fuels and gases, e.g. carbon dioxide. Specific extruded or molded thermoplastic articles are selected from the group consisting of pipes for transporting liquids and gases, inner linings for pipes, fuel lines, air break tubes, coolant pipes, air ducts, pneumatic tubes, hydraulic houses, cable covers, cable ties, connectors, canisters, and push-pull cables.

The present invention is further illustrated by the following examples. It should be understood that the following examples are for illustration purposes only, and are not used to limit the present invention thereto.

Methods

Compounding Method

Examples 1-3 and comparative examples C-1-C-3 were prepared by melt blending the ingredients listed in the Table in a Buss 55 mm extruder, operating at about 230° C. for PA1010 compositions and 250° C. for PA612 compositions, using a screw speed of about 180 rpm, and a throughput of 100 kg/hour. Ingredient quantities shown in the Table are given in weight percent on the basis of the total weight of the thermoplastic composition.

The compounded mixture was extruded in the form of laces or strands, cooled in a water bath, chopped into granules and placed into sealed aluminum lined bags in order to prevent moisture pick up. The cooling and cutting conditions were adjusted to ensure that the materials were kept below 0.15 wt % of moisture level.

Physical Properties Measurement

Mechanical tensile properties, i.e. E-modulus, stress at break (Tensile strength) and strain at break (elongation at break) were measured according to ISO 527-2/1A. Measurements were made on injection molded ISO tensile bar. The mold temperature was 70° C., and melt temperature was 230° C. for PA1010 and 250° C. for PA612 compositions.

The thickness of the test specimens was 4 mm and a width of 10 mm according to ISO 527/1A at a testing speed of 50 mm/min (tensile strength and elongation). Tensile Modulus was measured at 50 mm/min.

Air Oven Ageing (AOA)

The test specimens were heat aged in a re-circulating air ovens (Heraeus type UT6060) according to the procedure detailed in ISO 2578. At various heat aging times, the test specimens were removed from the oven, allowed to cool to room temperature and sealed into aluminum lined bags until ready for testing. The tensile mechanical properties were then measured according to ISO 527 using a Zwick tensile instrument. The average values obtained from 5 specimens are given in the Table.

Retention of strain at break corresponds to the percentage of the strain at break at 1008 hours and 2328 hours heat ageing in comparison with the value of specimens after heat aging for 72 hours considered as being 100%.

Materials

PA612 is Zytel® 158 NC010 resin, having a melting point of about 218° C., available from E. I. du Pont de Nemours and Company, Wilmington, Del.

PA1010 is Herox® polyamide resin available from E. I. du Pont de Nemours and Company, Wilmington, Del.

Surlyn®9320 copolymer refers to an ethylene/methacrylic acid copolymer, zinc neutralized, available from E.I. DuPont de Nemours and Company, Wilmington, Del., USA.

Elvaloy EP4934-4 refers to an ethylene/glycidyl methacrylate copolymer available from E.I. DuPont de Nemours and Company, Wilmington, Del., USA.

Colloids PE 48/93 refers to a carbon black dispersed in polyethylene available from Colloids Limited.

DPE refers to dipentaerythritol that was from Perstorp Speciality Chemicals AB, Perstorp, Sweden as Di-Penta 93.

Cu heat stabilizer refers to a mixture of 7 parts of potassium iodide and 1 part of copper iodide in 0.5 part of a stearate wax binder.

Irgafos® 168 stabilizer is a heat stabilizer available Ciba Speciality Chemicals Inc, Switzerland.

Irganox® 1098 stabilizer was available from Ciba Speciality Chemicals Inc, Switzerland.

Chimassorb® 944 refers to (poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidinyl)-imino]-1,6-hexanediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]]), supplied by Ciba Specialty Chemicals.

Tinuvin® 234 refers to a HALS available from Ciba Specialty Chemicals.

EXAMPLES 1-2 AND COMPARATIVE EXAMPLE C-1 AND C-2

Unreinforced PA1010 compositions of Examples 1 and 2 with DPE and Comparative Example C-1 and C-2 without DPE are listed in Table 1. Tensile properties after AOA at 150° C. at 72 h, 1008 h, and 2328 h, and % retention of strain at break are listed in Table 1. The examples showed greater than 80% retention of strain at break, after 1008 hours AOA at 150° C., as compared to the 72 h AOA control. These results are significantly better than the comparative examples having no DPE present.

EXAMPLES 3 AND COMPARATIVE EXAMPLE C-3

Unreinforced PA 612 compositions of Examples 3 with DPE and Comparative Example C-3 without DPE are listed in Table 1. Tensile properties after AOA at 150° C. at 72 h, 1008 h, and 2328 h, and % retention of strain at break are listed in Table 1. The example showed greater than 80% retention of strain at break, after 1008 hours AOA at 150° C., as compared to the 72 h AOA control. These results are significantly better than the comparative examples having no DPE present.

TABLE 1 Example C-1 1 C-2 2 C-3 3 PA612 76.4 73.4 PA1010 96.4 93.4 76.4 73.4 Surlyn ® 9320 16 16 16 16 Elvaloy ® EP4934-4 4 4 4 4 Colloids PE 48/93 2 2 2 2 2 2 Irganox ® 1098 0.3 0.3 0.3 0.3 0.3 0.3 Irgafos ® 168 0.3 0.3 0.3 0.3 0.3 0.3 Tinuvin ® 234 0.3 0.3 0.3 0.3 0.3 0.3 Chimassorb ® 944 0.3 0.3 0.3 0.3 0.3 0.3 Copper heat stabilizer 0.4 0.4 0.4 0.4 0.4 0.4 DPE 3 3 3 AOA 150° C., 72 h Tensile Modulus 2070 2110 1420 1380 1561 1552 Stress at Break 43 44 39 37 37 36 Strain at break 51 45 133 122 118 91 AOA 150° C., 1008 h Tensile Modulus 2240 2275 1471 1469 1703 1759 Stress at Break 43 46 39 35 41 45 Strain at break 41 40 76 102 75 75 Retention strain at break (%) 80 89 57 83 64 83 AOA 150° C., 2328 h Tensile Modulus 2243 2216 1492 1446 1679 1699 Stress at Break 58 56 43 46 42 51 Strain at break 15 35 56 63 4 41 Retention strain at break (%) 30 79 42 51 3 45 

1. A molded or extruded thermoplastic article comprising a polyamide composition comprising (a) a polyamide resin having a melting point and/or glass transition; (b) 0.1 to 10 weight percent of one or more polyhydric alcohols having more than two hydroxyl groups and having a number average molecular weight (M_(n)) of less than 2000; (c) 0 to 3 weight percent of a co-stabilizer, having a 10% weight loss temperature, as determined by thermogravimetric analysis, of greater than 30° C. below said melting point of said polyamide if said melting point is present, or at least 250° C. if said melting point is not present, said co-stabilizer selected from the group consisting of secondary aryl amines, hindered amine light stabilizers, and mixtures thereof; (d) 0 to less than 10 weight percent of one or more reinforcement agents; and (e) 0 to 50 weight percent polymeric toughener comprising a reactive functional group and/or a metal salt of a carboxylic acid; and wherein 4 mm test bars prepared from said polyamide composition, and exposed at an test temperature of 150° C. for a test period of about 1000 hours, in an atmosphere of air, and tested according to ISO 527-2/1A, have, on average, a retention of strain at break of greater than 80 percent, as compared with a control exposed at said test temperature for 72 hours; and with the proviso that the polyamide composition contains not more than 5 weight percent of a plasticizer; and, independently, with the further proviso that when said polyamide resin is selected from only a single polyamide having said melting point of at least 260° C., comprising greater than 95 mole percent semiaromatic repeat units derived from monomers selected from the group consisting of: one or more aromatic dicarboxylic acid(s) having 8 to 20 carbon atoms and one or more aliphatic diamine(s) having 4 to 20 carbon atoms; said aliphatic diamine(s) comprise less than 50 mole percent 2-methyl-1,5-pentanediamine.
 2. The molded or extruded thermoplastic article of claim 1 wherein said polyamide composition comprises one or more polyamides independently selected from the group consisting of Group (I) Polyamides having said melting point of less than 210° C., and comprising an aliphatic or semiaromatic polyamide selected from the group poly(pentamethylene decanediamide) (PA510), poly(pentamethylene dodecanediamide) (PA512), poly(ε-caprolactam/hexamethylene hexanediamide) (PA6/66), poly(ε-caprolactam/hexamethylene decanediamide) (PA6/610), poly(ε-caprolactam/hexamethylene dodecanediamide) (PA6/612), poly(hexamethylene tridecanediamide) (PA613), poly(hexamethylene pentadecanediamide) (PA615), poly(ε-caprolactam/tetramethylene terephthalamide) (PA6/4T), poly(ε-caprolactam/hexamethylene terephthalamide) (PA6/6T), poly(ε-caprolactam/decamethylene terephthalamide) (PA6/10T), poly(ε-caprolactam/dodecamethylene terephthalamide) (PA6/12T), poly(hexamethylene decanediamide/hexamethylene terephthalamide) (PA610/6T), poly(hexamethylene dodecanediamide/hexamethylene terephthalamide) (PA612/6T), poly(hexamethylene tetradecanediamide/hexamethylene terephthalamide) (PA614/6T), poly(ε-caprolactam/hexamethylene isophthalamide/hexamethylene terephthalamide) (PA6/6I/6T), poly(ε-caprolactam/hexamethylene hexanediamide/hexamethylene decanediamide) (PA6/66/610), poly(ε-caprolactam/hexamethylene hexanediamide/hexamethylene dodecanediamide) (PA6/66/612), poly(ε-caprolactam/hexamethylene hexanediamide/hexamethylene decanediamide/hexamethylene dodecanediamide) (PA6/66/610/612), poly(2-methylpentamethylene hexanediamide/hexamethylene hexanediamide/hexamethylene terephthamide) (PA D6/66//6T), poly(2-methylpentamethylene hexanediamide/hexamethylene hexanediamide/) (PA D6/66), poly(decamethylene decanediamide) (PA1010), poly(decamethylene dodecanediamide) (PA1012), poly(decamethylene decanediamide/decamethylene terephthalamide) (PA1010/10T) poly(decamethylene decanediamide/dodecamethylene decanediamide/decamethylene terephthalamide/dodecamethylene terephthalamide (PA1010/1210/10T/12T), poly(11-aminoundecanamide) (PA11), poly(11-aminoundecanamide/tetramethylene terephthalamide) (PA11/4T), poly(11-aminoundecanamide/hexamethylene terephthalamide) (PA11/6T), poly(11-aminoundecanamide/decamethylene terephthalamide) (PA11/10T), poly(11-aminoundecanamide/dodecamethylene terephthalamide) (PA11/12T), poly(12-aminododecanamide) (PA12), poly(12-aminododecanamide/tetramethylene terephthalamide) (PA12/4T), poly(12-aminododecanamide/hexamethylene terephthalamide) (PA12/6T), poly(12-aminododecanamide/decamethylene terephthalamide) (PA12/10T) poly(dodecamethylene dodecanediamide) (PA1212), and poly(dodecamethylene dodecanediamide/dodecamethylene dodecanediamide/dodecamethylene terephthalamide)) (PA1212/12T); Group (II) Polyamides having said melting point of at least 210° C., and comprising an aliphatic polyamide selected from the group consisting of poly(tetramethylene hexanediamide) (PA46), poly(ε-caprolactam) (PA 6), poly(hexamethylene hexanediamide/(ε-caprolactam/) (PA 66/6) poly(hexamethylene hexanediamide) (PA 66), poly(hexamethylene hexanediamide/hexamethylene decanediamide) (PA66/610), poly(hexamethylene hexanediamide/hexamethylene dodecanediamide) (PA66/612), poly(hexamethylene hexanediamide/decamethylene decanediamide) (PA66/1010), poly(hexamethylene decanediamide) (PA610), poly(hexamethylene dodecanediamide) (PA612), poly(hexamethylene tetradecanediamide) (PA614), poly(hexamethylene hexadecanediamide) (PA616), and poly(tetramethylene hexanediamide/2-methylpentamethylene hexanediamide) (PA46/D6); Group (III) Polyamides having said melting point of at least 210° C., and comprising (aa) about 20 to about 35 mole percent semiaromatic repeat units derived from monomers selected from one or more of the group consisting of: i. aromatic dicarboxylic acids having 8 to 20 carbon atoms and aliphatic diamines having 4 to 20 carbon atoms; and (bb) about 65 to about 80 mole percent aliphatic repeat units derived from monomers selected from one or more of the group consisting of: ii. an aliphatic dicarboxylic acid having 6 to 20 carbon atoms and said aliphatic diamine having 4 to 20 carbon atoms; and iii. a lactam and/or aminocarboxylic acid having 4 to 20 carbon atoms; Group (IV) Polyamides comprising (cc) about 50 to about 95 mole percent semiaromatic repeat units derived from monomers selected from one or more of the group consisting of: (i) aromatic dicarboxylic acids having 8 to 20 carbon atoms and aliphatic diamines having 4 to 20 carbon atoms; and (dd) about 5 to about 50 mole percent aliphatic repeat units derived from monomers selected from one or more of the group consisting of: (ii) an aliphatic dicarboxylic acid having 6 to 20 carbon atoms and said aliphatic diamine having 4 to 20 carbon atoms; and (iii) a lactam and/or aminocarboxylic acid having 4 to 20 carbon atoms; Group (V) Polyamides having said melting point of at least 260° C., and comprising (ee) greater than 95 mole percent semiaromatic repeat units derived from monomers selected from one or more of the group consisting of: i. aromatic dicarboxylic acids having 8 to 20 carbon atoms and aliphatic diamines having 4 to 20 carbon atoms; and (ff) less than 5 mole percent aliphatic repeat units derived from monomers selected from one or more of the group consisting of: ii. an aliphatic dicarboxylic acid having 6 to 20 carbon atoms and said aliphatic diamine having 4 to 20 carbon atoms; and iii. a lactam and/or aminocarboxylic acid having 4 to 20 carbon atoms; and Group (VI) Polyamides having no melting point and selected from the group consisting of poly(hexamethylene isophthalamide/hexamethylene terephthalamide) (6I/6T) and poly(hexamethylene isophthalamide/hexamethylene terephthalamide/hexamethylene hexanediamide) (6I/6T/66).
 3. The molded or extruded thermoplastic article of claim 2 wherein said polyamide resin is selected from Group (I) polyamides.
 4. The molded or extruded thermoplastic article of claim 2 wherein said polyamide resin is selected from Group (II) polyamides.
 5. The molded or extruded thermoplastic article of claim 2 wherein said polyamide resin is selected from Group (III) polyamides.
 6. The molded or extruded thermoplastic article of claim 2 wherein said polyamide resin is selected from Group (IV) polyamides.
 7. The molded or extruded thermoplastic article of claim 2 wherein said polyamide resin is selected from Group (V) polyamides.
 8. The molded or extruded thermoplastic article of claim 2 wherein said polyamide resin is selected from Group (VI) polyamides.
 9. The molded or extruded thermoplastic article of claim 1 wherein the co-stabilizer is present at 0.1 to 3 weight percent.
 10. The molded or extruded thermoplastic article of claim 2 wherein said polyamide resin comprises a blend of two or more polyamides selected from the group consisting of Group (I) and Group (II) Polyamides; Group (I) and Group (III) Polyamide, Group (I) and Group (VI) Polyamides, Group (II) and Group (III) Polyamides, Group (II) and Group (IV) Polyamides, Group (II) and Group (V) Polyamides, Group (II) and Group (VI) Polyamides, Group (III) and Group (VI) Polyamides, and Group (IV) and Group (V) Polyamides.
 11. The molded or extruded thermoplastic article of claim 10 wherein said polyamide resin comprises a blend of Group (II) and Group (V) Polyamides.
 12. The molded or extruded thermoplastic article of claim 10 wherein said polyamide resin comprises a blend of Group (II) and Group (III) Polyamides.
 13. The molded or extruded thermoplastic article of claim 1 wherein the polyhydric alcohol is selected from the group consisting of pentaerythritol, dipentaerythritol, tripentaerythritol, di-trimethylopropane, D-mannitol, D-sorbitol and xylitol.
 14. The molded thermoplastic article of claim 1 wherein said polyamide composition comprises less than 25 ppm copper as determined with atomic absorption spectroscopy.
 15. The molded or extruded thermoplastic article of claim 1 wherein the article is selected from the group consisting of pipes for transporting liquids and gases, inner linings for pipes, fuel lines, air break tubes, coolant pipes, air ducts, pneumatic tubes, hydraulic houses, cable covers, cable ties, connectors, canisters, and push-pull cables. 